Now I have had that problem with my sun conure, she has bitten my granddaughter on the lip. Sunny was on my shoulder and I turned my head around to give her a kiss when my granddaughter came over to get a kiss from her also. Sunny leaned out and bit her upper lip, didn't break the skin but scared me to death, I did not want her hurt or for it to leave a scar. She has been to the house since and if Sunny is on my shoulder she will lean out to get my granddaughter if she gets close enough, she lunges at her. I don't think she has done anything to her to make her dislike her that I know of, I guess she is jealous of her getting too close to me. I have to be careful from now on when she is here and I have Sunny out on my shoulder. Sunny is not that way with my grandson so go figure.